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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
71

Poly-acetylenes

Cook, Cyril Lloyd January 1951 (has links)
General methods for the synthesis of a wide range of hitherto unknown or inaccessible poly-acetylenic compounds (i.e. compounds containing a number of acetylenic bonds in conjugation) have been developed and a number of such compounds, containing up to six triple bonds in conjugation, have been synthesised. Since acetylenic and poly-acetylenic compounds continue to be isolated from natural sources, some attention has been given to the synthesis of model compounds as an aid to the elucidation of their structure. The poly-acetylenes are proving to be of fundamental interest to the theoretician and to the physical chemist. Infra-red and ultra-violet light absorption data have been obtained for a large variety of related compounds and are discussed, along with the data concerning other remarkable properties of these interesting substances.
72

The chemistry of the pentacyclic triterpenes with special reference to the lupeol group

Davy, Geoffrey Spencer January 1951 (has links)
No description available.
73

The photochemistry of phenyl sulphates : a contribution to the photochemistry of vat esters

Hill, Ronald January 1964 (has links)
A series of seven substituted phenyl sulphates, as model compounds for vat esters, were irradiated with U.V. light, in an attempt to elucidate the mechanism of their photolysis. The rates of photolysis were measured at various pH's in buffer solutions by following the liberation of sulphate, and were found to be first order with respect to the ester. With the exception of the meta-nitro ester, the esters containing electron donating substituents e.g.p-methyl and p-methoxy, reacted much ~aster than the ones containing electron attracting substituents. It was also found that e~ters containing electron donating substituents did not give 100% yields of sulphate at the end of the reaction, whereas the ones with electron attracting substituents did. It is thought that for all esters, except the m-nitro derivative, the reaction proceeds by a free radical mechanism, and this would seem to be confirmed by experiments with the p-chloro and p-methyl esters in the presence of the radical scavenger, acrylonitrile. No free sulphate at all appeared in irradiated solutions of the p-chloro ester, and ohly very small amounts with the p-methyl ester. A mechanism is postulated in which both -0-0- bond fission and -O-S- bond fission may occur, depending on the substituent. The latter mode of fission is thought to be absent in the case of p-nitro and p-chloro ester, but increases with the electron donating power of the substituent. The deviation from 100% yields of sulphate is explained by free radical sulphonation, arising from the formation of sulphite radical ions by -O-S- fission. The m-nitro ester is completely photo-hydrolysed rapidly, and a mechanism of solvolysis from the excited state is postulated. The work does not cast much light on the mechanism of photodevelopment of the vat esters, especially as little information was obtained of the fate of the organic radical species, but evidence of the formation of phenols from the esters was found, and it may be that photohydrolysis initiates the photo-development of vat esters.
74

Synthesis of benzoheterocycles using intramolecular cyclisation of aryl radicals

Jordan, Benjamin Marcus January 1990 (has links)
No description available.
75

The synthesis of rationally designed donor-acceptor dyads incorporating the boron dipyrromethene fluorophore

Clift, Sophie January 2013 (has links)
This thesis is concerned with the design, synthesis, characterisation and subsequent photophysical examination of dyads incorporating the boron dipyrromethane (bodipy) framework. Photodriven processes such as electron-, energy- and charge-transfer reactions are of the utmost importance in nature, with photosynthesis as a key example. Energy capturing arrays composed of intricate building blocks trap, transfer and store energy within a cell, employing a complex series of cascade-type reactions to channel this energy to the desired acceptor. Within this thesis, the theme of charge-transfer in particular is of principal focus and systems designed to investigate this phenomenon are examined. Chapter one presents an introduction to the bodipy fluorophore and the everexpanding field of artificial photosynthesis. In addition to this, the methods involved in analysing the distribution and movement of charge are discussed, as are the thought processes behind the rational design of molecules for specific functions. The second chapter serves as a detailed account of all the synthetic procedures undertaken. The chapter covers all the bodipy derivatives prepared, in addition to the precursors to these compounds and all additional materials synthesised. In chapters three to six, the rationale behind the design of each purpose built system is discussed, along with any preparative difficulties encountered and modifications to traditional synthetic protocol. Finally, the electrochemical properties of the compounds are analysed by cyclic voltammetry and their photophysics investigated by absorption and fluorescence spectroscopy. The data obtained is complimented by both appropriate NMR spectra and a discussion of crystal structural information obtained. In the case of the novel push-pull chromophore, JULBD, which is the principal focus of chapters three and four, the charge transfer capabilities of the dyad are analysed by correlating 13C chemical shift values with solvent polarity. This polarity dependence is further explored and analysed by solvent dependent absorption spectroscopy. In ii order to study the emissive properties, a temperature dependent fluorescence experiment was undertaken. Chapter five discusses the use of current catalytic methods to prepare a series of novel donor acceptor dyads and their precursor building blocks, introducing novel methodology for the synthesis of boronic esters including iridium and palladium catalysis. Finally, chapter six addresses the design rationale, synthesis and characterisation of a binaphthalene-spaced dyad incorporating the N,N-dimethylaniline moiety. This chapter also serves to introduce novel methodology which can be employed to execute bodipy sythesis employing the commonly used organic reagent formamide.
76

Oxidation of organotin compounds

Alleston, David Lawrence January 1961 (has links)
No description available.
77

The adsorption of methylsilane on Cu(111)

Ménard, Hervé January 2003 (has links)
No description available.
78

The lead tetra-acetate oxidations of enamines and indoles

Sukari, M. A. January 1981 (has links)
No description available.
79

Metal-mediated borylation of fluorocarbons

Lindup, Richard J. January 2006 (has links)
No description available.
80

The Thermal Decomposition of Amyl Phosphonium Salts, and of Amyl Bromides

Isaac, B. O. January 1977 (has links)
No description available.

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